Method for user relocation by home node B

ABSTRACT

A method for user relocation triggered by a Home NodeB Gateway (HGW) is provided, which comprises steps of: transmitting, by the HGW, a relocation request message to a Home NodeB (HNB) to which a User Equipment (UE) belongs; triggering, by the HNB, a relocation procedure to relocate the UE to another NodeB; and transmitting, by the HNB, a relocation response message corresponding to the relocation request message to the HGW. With the present invention, it is possible in a HNB system to implement a UE relocation triggered by a HGW for new scenarios. This scheme enhances the Iu-h interface and facilitates the improvement of service quality of users. Additionally, it is capable of providing users with continuous services in different scenarios. The present method is easy to implement and effective in improving the stability and performance of HNB system.

TECHNICAL FIELD

The present invention relates to mobile communication and particularly to relocation of user equipment (UE) in Home NodeB (HNB) communication system.

BACKGROUND ART

Conventionally, relocation is triggered by a UE measurement report. A radio network controller (RNC) determines whether or not to perform a handover or relocation based on analysis of the UE measurement report.

In a HNB system, the analysis of the UE measurement report is handled by the HNB. In a typical relocation procedure which is generally referred to as Outband Handover, a UE is relocated from a HNB to a macro NodeB.

In today's HNB system, application scenarios in which a user is relocated increase due to the increase in Home NodeB Gateway (HGW) and lu-h interface. In addition to the conventional relocation triggered by a UE measurement report, there is a need for a relocation which is triggered by a HGW and performed in cooperation with the HNB. For example:

1) When the HGW is reset, it is necessary to inform the HNB to reselect another HGW and relocate an existing user to a macro NodeB or another HNB which is capable of accept the user.

2) When the HGW detects a severe degradation on uplink service quality in the lu-h interface, it is necessary to improve the existing process to trigger the HNB to initiate a relocation process for the call of the user.

3) When a user who is currently being serviced is removed from the access control list by the administrator, the user can be relocated to a macro NodeB.

Therefore, in the existing lu-h or lu interface, there is no user relocation procedure initiated by an upper layer node.

DISCLOSURE OF INVENTION Technical Problem

The object of the present invention is to provide a user relocation procedure triggered by a HGW in a HNB system capable of satisfying new demands of new HNB scenarios.

Technical Solution

To achieve the object above, a method for user relocation triggered by a Home NodeB Gateway (HGW) is provided, which comprises steps of transmitting, by the HGW, a relocation request message to a Home NodeB (HNB) to which a User Equipment (UE) belongs; triggering, by the HNB, a relocation procedure to relocate the UE to another NodeB; and transmitting, by the HNB, a relocation response message corresponding to the relocation request message to the HGW.

Advantageous Effects

With the present invention, it is possible in a HNB system to implement a UE relocation triggered by a HGW for new scenarios. This scheme enhances the lu-h interface and facilitates the improvement of service quality of users. Additionally, it is capable of providing users with continuous services in different scenarios. The present method is easy to implement and effective in improving the stability and performance of HNB system.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a structure of a HNB system.

FIG. 2 illustrates a user relocation triggered by reset of a HGW.

FIG. 3 illustrates a user relocation triggered by degradation of service quality in an lu-h interface.

FIG. 4 illustrates a user relocation triggered by ACL update.

FIG. 5 illustrates a typical relocation procedure.

MODE FOR THE INVENTION

The detailed procedure of a HGW-initiated user relocation in which a UE is relocated from a HNB to a macro NodeB is provided according to the present invention.

As illustrated in FIG. 1, a UE accesses a signaling system No. 7 network via a home-located HNB. Based on signaling bear functionality provided by the HNB and a HGW, the UE performs signaling interaction with a core network node, Serving GPRS Supporting Node (SGSN)/Mobile Switching Center (MSC), to control the communication with external devices.

The TS25.331 protocol and a conventional air interface (UU Interface) are adopted between the UE and the HNB. A lu-home interface is adopted between the HNB and the HGW. So far, the control protocol for the lu-home (which is referred to as lu-h) interface is still under development. The signaling interaction and transfer between the UE and the core network is conducted between the HGW and the MSC/SGSN using the conventional lu interface based on the TS25.413 protocol.

According to the present invention, a method of UE relocation triggered by the HGW is provided. This method satisfies the mobility requirements in such cases where the HGW is reset, the service quality in the lu-h interface is degraded, and the user is removed from the access control list (ACL) by the administrator. Thus, it is ensured that the user can continue to be serviced by the operator without interruption in such cases.

According to the present invention, a user relocation request/response message is added in the lu-h interface. The HGW transmits the relocation request message to each HNBs. The HNB initiates a typical relocation process according to the contents of the relocation request. After completion of the relocation process, the HNB transmits a relocation response message to the HGW. The contents of the relocation request message are shown in Table 1.

TABLE 1 Contents of user relocation request message Level 1 member Level 2 member Transaction ID Number of Relocation User Relocation User Information List User Call ID IMSI Relocation Cause

In Table 1, Transaction ID, which is the ID of each transaction, is used to prevent from processing same relocation request repeatedly. Number of Relocation User is the number of users to be relocated indicated in the message. Relocation User Information List indicates the information on individual users to be relocated. User Call ID is used to uniquely identify the user in the HNB. IMSI is the International Mobile Subscriber Identity of the user. Relocation Cause indicates the cause of relocation which includes three possibilities as shown in Table 2.

TABLE 2 User relocation cause Relocation Cause Home NodeB Gateway Reset Degradation of Service Quality of uplink direction in lu-h interface Removed from ACL

The contents of the user relocation response message are shown in Table 3.

TABLE 3 Contents of user relocation response message Level 1 member Level 2 member Transaction ID Number of Relocation User Relocation Result List User Call ID Relocation Result Fail Cause

In Table 3, Transaction ID corresponds to that in the relocation request message. Number of Relocation User is the number of users to be relocated indicated in the message. Relocation Result List indicates the result information on individual relocated users. User Call ID is use to uniquely identify the user in the HNB. Relocation Result indicates the result of relocation, with 0 indicating a success and 1 indicating a failure. If the relocation fails, the cause of the failure will be indicated in Fail Cause.

TABLE 4 Cause of user relocation failure Fail Cause Home NodeB Internal Error No Marco Service Not Existing

The First Embodiment

A user relocation procedure triggered by the reset of the HGW is illustrated in FIG. 2.

The reset of the HGW can be triggered by software/hardware abnormity within the HGW or external requirement such as routing software updated by the administrator. Prior to the reset, the HGW determines if there is a user currently being serviced based on its internal software detection mechanism. If so, the HGW constructs a relocation request message in which the Relocation Cause is set as HGW Reset and the Transaction ID corresponding to the message is recorded. Then the HGW transmits the relocation request message to a HNB to which the user belongs and waits for a response message from the HNB.

After receiving the relocation request message from the HGW, the HNB records the Transaction ID of the message and determines whether the Relocation Cause for the user is HGW Reset. If so, the HNB determines whether the service for the user exists in the HNB according to the user's IMSI. If the service does not exist, the HNB rejects the relocation request and transmits to the HGW a relocation response message in which the Fail Cause is set as Service not existing. If the service does exist in the HNB, the HNB further determines if there is a macro NodeB to which the user can be relocated. If there is such a macro NodeB, the HNB initiates a typical relocation process to relocate the user from the HNB to the macro NodeB. Information on the cell of the macro NodeB which is also covered by the HNB can be informed to the HNB by an entity for the operation, maintenance and administration of the network during initial registration of the HNB. If there is no such a macro NodeB, the HNB rejects the relocation request and transmits a relocation response message in which the Fail Cause is set as No Marco to indicate that there is no macro NodeB for relocating to. For other causes for the failure of the relocation, the Fail Cause in the response message can be set as HNB Internal Error.

With reference to FIG. 5, a typical relocation process can be described in detail, which comprises following steps.

1> The HNB transmits a Relocation Required message to SGSN/MSC.

2> The SGSN/MSC transmits a relocation request message to the macro radio network controller requiring the latter to prepare for the relocation.

3> The macro radio network controller initiates a setup procedure for a user plane bearer in the lu interface.

4> The macro radio network controller transmits a relocation request acknowledge message to the SGSN/MSC indicating that the resources for the relocation have been prepared. The message includes reconfiguration information notifying the HNB to use specifically which of the following processes to facilitate the relocation: radio bearer setup, radio bearer release, radio bearer reconfiguration, transmission channel reconfiguration, and physical channel reconfiguration.

5> The SGSN/MSC transmits an relocation command message to the HNB informing the HNB to perform relocation.

6> The HNB transmits a physical channel reconfiguration message (or a message such as radio bearer setup, radio bearer release, radio bearer reconfiguration, and transmission channel reconfiguration, depending on the designation in the previous response message from the macro radio network controller) to UE informing the UE of new physical channel parameters.

7> After successfully accessing the target macro radio network controller, the UE transmits a physical channel reconfiguration complete message to the target macro radio network controller indicating that the handover is completed.

8> The target macro radio network controller transmits a relocation complete message to the SGSN/MSC indicating that the relocation is completed.

9> The SGSN/MSC transmits an lu release command message to the original HNB requiring the HNB to release the lu connection.

10> The HNB initiates a release procedure for user plane bearer in the lu interface.

11> The HNB transmits a lu release complete message to the SGSN/MSC indicating the release of lu.

The Second Embodiment

A user relocation procedure triggered by degradation of uplink service quality in lu-h interface is described in detail below.

In a HNB system, the protocols used between the HNB and a core network are RTP protocol for circuit switch domain user plane bearer and GTP protocol for the packet switch domain user plane bearer, respectively. In a HNB system, IP protocol is utilized as a lower layer transmission protocol for RTP and GTP. It is required by 3GPP specifications that a RTP or GTP datagram is transmitted at the transmitter side with the serial number field in the datagram header incremented during transmission. At the receive side, the link quality can be detected by monitoring the serial number field of the RTP/GTP datagram header such that disordered datagram can be dropped.

In a HNB system, for the downlink, the HNB can detects the link service quality by monitoring the serial number field of the RTP/GTP datagram header such that a Relocation Required message can be constructed to request the core network to initiate relocation process if there is a severe degradation of link service quality. For the uplink, however, it is problematic that the core network cannot autonomously initiate a relocation process even if a severe degradation of link service quality is detected, since the relocation process can only be initiated by the source RNC. In a HNB system, the source RNC is the HNB which, however, does not know the fact that the uplink service quality is severely degraded.

With reference to FIG. 3, when detecting that uplink service quality in the lu-h interface is degraded for one or more UEs, the HGW constructs a relocation request message in which a corresponding relocation cause is filled and Transaction ID corresponding to the message is recorded. Then the HGW transmits the relocation request message to a HNB to which the user belongs and waits for a response message from the HNB.

After receiving the relocation request message from the HGW, the HNB records the Transaction ID of the message and determines whether the Relocation Cause for the user is Degradation of Service Quality of uplink direction in lu-h interface. If so, the HNB determines whether the service for the user exists in the HNB according to the user's IMSI. If the service does not exist, the HNB rejects the relocation request and transmits to the HGW a relocation response message in which the Fail Cause is set as Service not existing. If the service does exist in the HNB, the HNB further determines if there is a macro NodeB to which the user can be relocated. If there is such a macro NodeB, the HNB initiates a typical relocation process to relocate the user from the HNB to the macro NodeB. Information on the cell of the macro NodeB which is also covered by the HNB can be informed to the HNB by an entity for the operation, maintenance and administration of the network during initial registration of the HNB. If there is no such a macro NodeB, the HNB rejects the relocation request and transmits a relocation response message in which the Fail Cause is set as No Marco to indicate that there is no macro NodeB for relocating to. For other causes for the failure of the relocation, the Fail Cause in the response message can be set as HNB Internal Error.

The Third Embodiment

A user relocation procedure triggered by ACL update is described in detail below.

An administrator or authorized user can initiate a maintenance process for ACL including adding or removing a user from the ACL. When a friend drops in, for example, the host as an authorized user may add the friend to the ACL temporarily and remove him from the ACL after the he leaves. With respect to the friend, if he is removed from the ACL by the administrator or authorized user while being serviced by the HNB of the host, his service should not be terminated if there is a macro NodeB in proximity which can provide the service. In this case, it is reasonable to relocate the user to the macro NodeB.

With reference to FIG. 4, the administrator or authorized user logs into a HNB Configuration Server (HCS) using web or any other approaches to issue an instruction to remove a user from the ACL. In this case, the HCS transmits an ACL update request message to the HGW instructing the HGW to remove the UE from the ACL. At this point, the HGW determines whether the user is currently being serviced according to the user ID (or IMSI) in the message. If not, the ACL can be directly updated. If the service exists, the HGW initiates a relocation process for the user. The HGW constructs a relocation request message in which the Relocation Cause is set as Removed from ACL and the Transaction ID corresponding to the message is recorded. Then the HGW transmits the relocation request message to a HNB to which the user belongs and waits for a response message from the HNB.

After receiving the relocation request message from the HGW, the HNB records the Transaction ID of the message and determines whether the Relocation Cause for the user is removed from ACL. If so, the HNB determines whether the service for the user exists in the HNB according to the user's IMSI. If the service does not exist, the HNB rejects the relocation request and transmits to the HGW a relocation response message in which the Fail Cause is set as Service not existing. If the service does exist in the HNB, the HNB further determines if there is a macro NodeB to which the user can be relocated. If there is such a macro NodeB, the HNB initiates a typical relocation process to relocate the user from the HNB to the macro NodeB. Information on the cell of the macro NodeB which is also covered by the HNB can be informed to the HNB by an entity for the operation, maintenance and administration of the network during initial registration of the HNB. If there is no such a macro NodeB, the HNB rejects the relocation request and transmits a relocation response message in which the Fail Cause is set as No Marco to indicate that there is no macro NodeB for relocating to. For other causes for the failure of the relocation, the Fail Cause in the response message can be set as HNB Internal Error. 

The invention claimed is:
 1. A method for user relocation, the method comprising steps of: receiving, by a Home NodeB (HNB) to which a User Equipment (UE) belongs, a relocation request message transmitted from a Home NodeB Gateway (HGW), the relocation request message including an indication that an access control list is to be updated or changed, where a relocation of the UE is triggered by an access control list update request transmitted to the HGW by an HNB configuration server; determining, by the HNB, whether or not the UE is currently using a service on the HNB when the relocation request message is received from the HGW; identifying, by the HNB, that the UE is capable of being relocated to a macro NodeB, if the UE is currently using the service on the HNB; performing, by the HNB, a relocation procedure to relocate the UE by configuring resources for the relocation with the macro NodeB, if the UE is capable of being relocated to the macro NodeB; and transmitting, by the HNB, a relocation response message corresponding to the relocation request message to the HGW, after performing the relocation procedure.
 2. The method of claim 1, further comprising step of: obtaining, by the HGW, information on update of an access control list.
 3. The method of claim 1, wherein the relocation request message comprises a relocation cause.
 4. The method of claim 3, wherein the relocation cause comprises one of an HGW reset, degradation of service quality in an lu-h interface, and an access control list update.
 5. The method of claim 1, further comprising step of: obtaining, by the HNB, information on the macro NodeB from a network.
 6. The method of claim 1, wherein the relocation request message comprises an identification of the UE.
 7. The method of claim 1, further comprising transmitting the relocation response message comprising a fail cause set as service not existing, if the service for the UE does not exist.
 8. The method of claim 1, further comprising transmitting the relocation response message comprising a fail cause set as no macro NodeB, if there is no macro NodeB to relocate the UE to. 